Recent factory automation (FA) systems use an industrial field network (IFNW) of Ethernet (registered trademark) between FA controllers and between an FA controller and an I/O. Hereinafter, the FA controller is called a “master station”, and the I/O is called a “slave station”.
In a case in which a master station controls multiple slave stations, devices are connected to each other in a line type network topology for saving wires. Such an industrial field network performs transmission and reception of frames using token frames in accordance with the type of protocol.
A system such as a servo system may be required to have synchronization characteristic and real-time responsiveness. In this system, a processing time from when a slave station receives a token frame addressed to its own station until when the slave station transmits a token frame to the next station is reduced to shorten the tact time, thereby improving the productivity per unit time.
Thus, in a case of protocol using token frames, the time from when a station receives a token frame addressed to its own station until when the station transmits a token frame to the next station is important.
After receiving a token frame, a typical slave station in such a system adds a frame check sequence (FCS) to the token frame to generate a dedicated frame by using dedicated hardware such as an application specific integrated circuit (ASIC). The slave station transmits its own data in the generated dedicated frame and immediately transmits a token frame to the next station. This processing is executed independently of software processing. Thus, using dedicated hardware enables generation of a dedicated frame independently of software, thereby allowing a constructing an FA system that has superior synchronization characteristic and high real-time responsiveness.
An IFNW that allows constructing such a highly precise FA system having superior synchronization characteristic and high real-time responsiveness is disclosed in PTL 1.